Leases - annual minimum rental commitments (Details) $ in Millions	Aug. 31, 2017 USD ($)
Finance Lease Obligation [Abstract]
2018	$ 18
2019	18
2020	18
2021	18
2022	18
Later	235
Total minimum lease payments	325
Capital Lease [Abstract]
2018	62
2019	60
2020	59
2021	58
2022	56
Later	915
Total minimum lease payments	1,210
Operating Lease [Abstract]
2018	3,210
2019	3,045
2020	2,844
2021	2,605
2022	2,371
Later	18,736
Total minimum lease payments	$ 32,811

Amount of minimum lease payments for capital leases.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6455398&loc=d3e45280-112737

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Amount of minimum lease payments for capital leases due in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 55
-Paragraph 40
-Subparagraph (Note 3)
-URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697

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-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (a)
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-SubTopic 20
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-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
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-Section 55
-Paragraph 40
-Subparagraph (Note 3)
-URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697

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